Archive for the ‘chemistry’ Category

Enlarge/ A detail from "Untitled" (1981) by Jean-Michel Basquiat, as viewed under normal light (left) and UV light (right). Note the hidden arrow between the letters "E" and "P." (credit: Longevity Art Preservation)

Jean-Michel Basquiat, the late neo-expressionist whose tragic life story inspired a 1996 film, used invisible ink to draw secret figures in at least one of his early paintings, Artnet News reported last month. The figures are easily visible under UV light, and more of the artist's work from this period may contain such hidden drawings.

Invisible ink has been around since at least the fourth century BC; it's mentioned in a treatise on secret communications by Aeneas Tacticus. It's familiar to anyone who has ever gotten their hand stamped when they entered a club so they could be readmitted later by holding it under UV light. There are many different types, but substances that glow in response to UV light include lemon juice, body fluids (hence the use of UV light in forensics), sunscreen, and some soaps and laundry detergents.

But invisible ink is rarely used by artists. One notable exception is the Chinese-born British artist Aowen Jin, whose 2015 exhibit at London's Horniman Museum featured a series of hand-drawn invisible-ink illustrations, which can only be seen under UV light, on the walls and floor of the Music Gallery Performance Space. Apparently, Basquiat sometimes used fluorescent materials, and signed one 1982 canvas, Orange Sports Figure, in invisible ink. But this is the first known instance of the artist intentionally embedding secret drawings into a painting.

Enlarge/ Regional differences in the aromatic compounds found in hop varieties can significantly affect the taste of craft beers. (credit: DEA/G. Wright/Getty Images)

If you're a fan of craft beer with a strong, hoppy flavor, heed the science that says to store your beer in a cool place and drink it within three months or so, lest it lose that rich aroma. That's one of the key takeaways from a new study by German scientists published in the journal Brewing Science.

All beer contains hops, a key flavoring agent that also imparts useful antimicrobial properties with its rich aroma. (Without them, beer spoils quickly.) To make beer, brewers mash and steep grain in hot water, which converts all that starch into sugars. This is traditionally the stage where hops are added to the liquid extract (wort) and boiled to give the beer that hint of bitterness. That turns some of the resins (alpha acids) in the hops into iso-alpha acids, producing a bitter taste. Yeast is then added to trigger fermentation, turning the sugars into alcohol.

Add too many hops, however, and the beer will be so bitter as to be undrinkable. So in recent years, many craft brewers have started using dry-hopping as a way to put more hops in beer without getting excessive bitterness. It's added during or after the fermentation stage, after the wort has cooled. There is no isomerization of the alpha acids, so you get all that aromatic hoppy flavor without too much bitterness. Brewers can use as much as 20 times the usual amount of hops if they're dry-hopping. (Just beware of "hop creep," which can cause such bottled beers to explode.)

Enlarge/ The 1861 notebook of Sir William Crookes, containing all his data on thallium samples. (credit: SSPL/Getty Images)

There's rarely time to write about every cool science story that comes our way. So this year, we're running a special Twelve Days of Christmas series of posts, highlighting one story that fell through the cracks each day, from December 25 through January 5. First up: a tale of attempted murder and the geologist who hopes he can help solve the case.

A new trace analysis of the victim's hair sheds fresh light on a famous unsolved cold case by establishing a timeline for the thallium poisoning of Chinese college student Zhu Ling in 1994. Published in October in the journal Forensic Science International, the work could one day lead to catching the culprit, and could help solve future heavy-metal poisonings.

Zhu Ling was a sophomore majoring in physical chemistry at Tsinghua University in Beijing, China, when she mysteriously began losing hair, with accompanying stomach pain and muscle paralysis, sinking into a coma four months later. Doctors were initially baffled, but friends posted her symptoms to a Usenet group, drawing attention to Zhu Ling's plight—likely the first telemedicine trial. Physicians around the world agreed the likely cause was thallium poisoning (a toxic heavy metal sometimes used in rat poison), and her doctors treated her with the commercial dye Prussian blue, the most common antidote.

Update: It's Thanksgiving in the US, and Ars staffers are off experimenting in the kitchen rather than on the page. Actually, sometimes we experiment in the kitchen in order to put it on the page, too—like this 2013 series on home brewing some delightfully autumnal hard cider. While it's too late to get the job done for today's big meal, allow this guide to inspire you for your large winter gatherings. This piece originally ran on October 19, 2013, and it appears unchanged below.

My relationship with beer has grown too comfortable. We share an easy routine: I buy it at the store—a different kind almost every time—take it home, and drink it. I'm not sure how the beer feels about this, but it seems happy. Still, things have gotten boring. So I'm taking the next step: making my own hard cider.

I chose cider for my first foray into home brewing for a couple of reasons. First, much as I would like to make beer, it involves a more extended process and more specialized ingredients. Wine is closer to cider in simplicity, but I envision cheaply made homebrewed wine tasting much worse than cheaply made cider. Furthermore, autumn comes but once a year; I can buy a wine or beer kit any time, but there’s only a couple of months during which I can get good soft cider.

Enlarge/ The breathing of the crowd: The 2015 found-footage horror film Paranormal Activity: Ghost Dimension was one of the movies screened during the study. (credit: Paramount Pictures)

Parents of young children often struggle to assess how upsetting a particular film will be for their offspring. Ratings systems can help, but tend to be subjective assessments. It might soon be possible to objectively evaluate how intense films might be for younger viewers just by analyzing the chemicals that audiences emit when they breathe, according to a new study by researchers from the Max Plank Institute for Chemistry in Mainz, Germany. They described their findings in a new paper in PLoS ONE.

Sure, it seems bit far-fetched, but tracking the emission of volatile organic compounds (VOCs) is an active and entirely legitimate area of research. Plastics, for instance, emit VOCs as they degrade over time, thanks to exposure to light, heat, moisture, and pollutants. This so-called "off-gassing" results in a serious issue for museum conservationists and libraries, among others.

Every country has its own rating system for films, designed to guide consumers as to what kinds of content they might encounter while watching a given film. While such systems are supposedly based on objective criteria—how much violence, sexual content, and bad language is included—there is actually quite a bit of subjective variability involved in making these determinations. And the public's sensibilities can shift over time: films that were deemed shocking in the 1930s strike today's audiences as remarkably tame. It matters because a film's rating has a direct impact on how broad an audience it can reach.

Enlarge/ That lovely blue exterior could be hiding a heart of diamond. (credit: NASA)

Carbon, oxygen, and nitrogen are some of the easiest heavier elements to form through fusion. As a result, they’re common in our Solar System, typically found combined with hydrogen to make ammonia, water, and methane. In the gas and ice giants of the outer Solar System, however, these chemicals are placed under extreme pressures, where chemistry starts to get a bit weird. Do these chemicals survive the crushing interiors of these planets?

One intriguing idea is that methane doesn’t survive. As pressure and temperature increase, methane should start condensing into more complex hydrocarbons. Then, as pressures increase further, calculations indicate the hydrogen and carbon should separate out, leaving pure carbon to sink to the depths of these planets. As a result, it’s been hypothesized that, close to their core, planets like Neptune and Uranus have a layer of pure diamond.

While some evidence supporting this theory has surfaced over the years, it’s been hard to precisely replicate the temperatures and pressures found inside the planets. Now, new work done at the SLAC X-ray laser facility supports the idea that these planets are full of diamonds. But the work indicates the diamonds only form at greater depths than we’d previously thought.

Randall Munroe, creator of popular webcomic XKCD, recently published a new book called Thing Explainer: Complicated Stuff in Simple Words, in which he uses only the thousand most common words in the English language to explain how a variety of things work, from locks to nuclear bombs. Monroe’s publisher, Houghton Mifflin Harcourt, also publishes textbooks, and when editors in the textbook division saw proofs of Monroe’s Thing Explainer, they realized that his simple explanations could be used to augment high school textbooks.

You know, the old strategy employed ineffectively by dad joke-tellers everywhere: get the #teens on your side with humor.

(credit: Randall Munroe)

Luckily, Munroe’s Thing Explainer comics are absurd enough in their hyper-simplicity that they have a shot at breaking down the walls of sarcasm and ennui encircling the most eye-rolling of high school students.